The present invention relates in general to sewer pipes and in particular to a method of and a device for making a canalization provided with working shafts or trenches through which a string of sewer pipes is pressed forwards in a water-conductive ground defining an underground water level.
In making canals provided with working shafts or trenches according to the pressing method in a water-conductive ground, the underground water level has hitherto been lowered to such a degree that upon working the shaft or trenches and upon the subsequent pressing of the string of sewer pipes by means of an open cutting shoe, the front ends thereof could be pressed in the ground without the application of a pressure chamber; alternatively, in the case when such a large lowering of the underground water level was not possible, the front end of the sewer pipe string immediately behind the cutting shoe was provided with a locking arrangement with a pressure chamber.
The latter arrangement however encounters considerable operational difficulties due to the fact that pressure in the pressure chamber must counteract pressure of the surrounding water in order to prevent the penetration of water into the cutting shoe. According to existing safety regulations and rules governing working conditions in pressure chambers, the crews attending the driving of the pipe underground can work only shorter shifts; moreover, the lock arrangement considerably interferes with the discharge of sod falling in the cutting shoe in the range of the pressure chamber, and altogether a considerable increase of manufacturing costs for canalization of this kind will result.